Category: ADFS

Introduction

Additional nodes in an ADFS farm are required to provide redundancy incase your primary ADFS node goes offline. This ensures your ADFS service is still up and servicing all incoming requests. Additional nodes also help in load balancing the incoming traffic, which provides a better user experience in cases of high authentication traffic.

Overview

Once an ADFS farm has been created, adding additional nodes is quite simple and mostly relies on the same concepts for creating the ADFS farm. I would suggest reading my previous blog Automate ADFS Farm Installation and Configuration as some of the steps we will use in this blog were documented in it.

In this blog, I will show how to automatically provision a secondary ADFS node to an existing ADFS farm. The learnings in this blog can be easily used to deploy more ADFS nodes automatically, if needed.

Install ADFS Role

After provisioning a new Azure virtual machine, we need to install the Active Directory Federation Services role on it. To do this, we will use the same Desired State Configuration (DSE) script that was used in Automate ADFS Farm Installation and Configuration. Please refer to the section Install ADFS Role in the above blog for the steps to create the DSE script file InstallADFS.ps1.

Add to an existing ADFS Farm

Once the ADFS role has been installed on the virtual machine, we will create a Custom Script Extension (CSE) to add it to the ADFS farm.

In order to do this, we need the following

certificate that was used to create the ADFS farm

ADFS service account username and password that was used to create the ADFS farm

Once the above prerequisites has been met, we need a method for making the files available to the CSE. I documented a neat trick to “sneak-in” the certificate and password files onto the virtual machine by using Desired State Configuration (DSE) package files in my previous blog. Please refer to Automate ADFS Farm Installation and Configuration under the section Create ADFS Farm for the steps.

Also note, for adding the node to the adfs farm, the domain user credentials are not required. The certificate file will be named adfs_certificate.pfx and the file containing the encrypted adfs service account password will be named adfspass.key.

Assuming that the prerequisites have been satisfied, and the files have been “sneaked” onto the virtual machine, lets proceed to creating the CSE.

Open Windows Powershell ISE and paste the following.

param (
$DomainName, $PrimaryADFSServer, $AdfsSvcUsername
)

The above shows the parameters that need to be passed to the CSE where

$DomainName is the name of the Active Directory domain$PrimaryADFSServer is the hostname of the primary ADFS server$AdfsSvcUsername is the username of the ADFS service account

Save the file with a name of your choice (do not close the file as we will be adding more lines to it). I named my script AddToADFSFarm.ps1

Next, we need to define a variable that will contain the path to the directory where the certificate file and the file containing the encrypted adfs service account password are stored. Also, we need a variable to contain the key that was used to encrypt the adfs service account password. This will be required to decrypt the password.

Now, we need to import the certificate into the local computer certificate store. To make things simple, when the certificate was exported from the primary ADFS server, it was encrypted using the adfs service account password.

After importing the certificate, we will read it to get its thumbprint.

Up until now, the steps are very similar to creating an ADFS farm. However, below is where the steps diverge.

Add the following lines to add the virtual machine to the existing ADFS farm

You now have a custom script extension file that will add a virtual machine as a secondary node to an existing ADFS Farm.

Below is the full CSE

All that is missing now is the method to bootstrap the scripts described above using Azure Resource Manager templates.

Below is the ARM template that can be used to install ADFS role on the a virtual machine and then add this virtual machine as a secondary node to the ADFS farm

In the above ARM template, the parameter ADFS02VMName refers to the hostname of the virtual machine that will be added to the ADFS Farm.

Listed below are the variables that have been used in the ARM template above

The above method can be used to add as many nodes to the ADFS farm as needed.

I hope this comes in handy when creating an ARM template to automatically deploy an ADFS Farm with additional nodes.

Introduction

In this multi-part blog, I will be showing how to automatically install and configure a new ADFS Farm. We will accomplish this using Azure Resource Manager templates, Desired State Configuration scripts and Custom Script Extensions.

Overview

We will use Azure Resource Manager to create a virtual machine that will become our first ADFS Server. We will then use a desired state configuration script to join the virtual machine to our Active Directory domain and then to install the ADFS role. Finally, we will use a Custom Script Extension to install our first ADFS Farm.

Install ADFS Role

We will be using the xActiveDirectory and xPendingReboot experimental DSC modules.

After downloading, unzip the file and place the contents in the Powershell modules directory located at $env:ProgramFiles\WindowsPowerShell\Modules (unless you have changed your systemroot folder, this will be located at C:\ProgramFiles\WindowsPowerShell\Modules )

Open your Windows PowerShell ISE and lets create a DSC script that will join our virtual machine to the domain and also install the ADFS role.

Copy the following into a new Windows Powershell ISE file and save it as a filename of your choice (I saved mine as InstallADFS.ps1)

In the above, we are declaring some mandatory parameters and some variables that will be used within the script

$MachineName is the hostname of the virtual machine that will become the first ADFS server

$DomainName is the name of the domain where the virtual machine will be joined

$AdminCreds contains the username and password for an account that has permissions to join the virtual machine to the domain

$RetryCount and $RetryIntervalSec hold values that will be used to check if the domain is available

We need to import the experimental DSC modules that we had downloaded. To do this, add the following lines to the DSC script

Import-DscResource -Module xActiveDirectory, xPendingReboot

Next, we need to convert the supplied $AdminCreds into a domain\username format. This is accomplished by the following lines (the converted value is held in $DomainCreds )

Next, we need to tell DSC that the command needs to be run on the local computer. This is done by the following line (localhost refers to the local computer)

Node localhost

We need to tell the LocalConfigurationManager that it should continue with the configuration after a reboot, reboot the server if needed and to just apply the settings only once (DSC can apply a setting and constantly monitor it to check that it has not been changed. If the setting is found to be changed, DSC can re-apply the setting. In our case we will not do this, we will apply the setting just once).

Next, we need to check if the Active Directory domain is ready. For this, we will use the xWaitForADDomain function from the xActiveDirectory experimental DSC module.

Once we know that the Active Directory domain is available, we can go ahead and join the virtual machine to the domain.

the JoinDomain function depends on xWaitForADDomain to finish successfully. If xWaitForADDomain fails, JoinDomain will not run

Once the virtual machine has been added to the domain, it needs to be restarted. We will use xPendingReboot function from the xPendingReboot experimental DSC module to accomplish this

Next, we will install the ADFS role on the virtual machine

Our script has now successfully added the virtual machine to the domain and installed the ADFS role on it. You now have to create a zip file with InstallADFS.ps1 and upload it to a location that Azure Resource Manager can access (I would recommend uploading to GitHub). Include the xActiveDirectoryand xPendingRebootexperimental DSC modules. Also add a folder called Certificatesinside the zip file and put the ADFS certificate and the encrypted password files (discussed in the next section) inside the folder.

In the next section, we will configure the ADFS Farm.

The full InstallADFS.ps1 DSC script is pasted below

Create ADFS Farm

Once the ADFS role has been installed, we will use Custom Script Extensions (CSE) to create the ADFS farm.

One of the requirements to configure ADFS is a signed certificate. I used a 90 day trial certificate from Comodo.

There is a trick that I am using to make my certificate available on the virtual machine. If you bootstrap a DSC script to your virtual machine in an Azure Resource Manager template, the script along with all the non out-of-box DSC modules have to be packaged into a zip file and uploaded to a location that ARM can access. Then, before ARM uses the script, it downloads the zip file and unzips it, and copies the directories inside the zip file to $env:ProgramFiles\WindowsPowerShell\Modules ( C:\ProgramFiles\WindowsPowerShell\Modules )

I am using this feature to sneak my certificate on to the virtual machine. I create a folder called Certificates inside the zip file containing the DSC script and put the certificate inside it. Also, I am not too fond of passing plain passwords from my ARM template to the CSE, so I created two files, one to hold the encrypted password for the domain administrator account and the other to contain the encrypted password of the adfs service account. These two files are named adminpass.key and adfspass.key and will be placed in the Certificates folder within the zip file.